Retry count for validate links task

core/src/main/scala/com/lightbend/paradox/ParadoxProcessor.scala

@@ -19,10 +19,10 @@ package com.lightbend.paradox
 import com.lightbend.paradox.template.PageTemplate
 import com.lightbend.paradox.markdown._
 import com.lightbend.paradox.tree.Tree.{ Forest, Location }
+
 import java.io.{ File, FileOutputStream, OutputStreamWriter }
 import java.nio.charset.StandardCharsets
-
-import org.jsoup.Jsoup
+import org.jsoup.{ Connection, Jsoup }
 import org.jsoup.nodes.Document
 import org.pegdown.ast._
 
@@ -108,6 +108,7 @@ class ParadoxProcessor(reader: Reader = new Reader, writer: Writer = new Writer,
     groups:           Map[String, Seq[String]],
     properties:       Map[String, String],
     ignorePaths:      List[Regex],
+    retryCount:       Int,
     validateAbsolute: Boolean,
     logger:           ParadoxLogger): Int = {
 
@@ -151,7 +152,7 @@ class ParadoxProcessor(reader: Reader = new Reader, writer: Writer = new Writer,
               reportErrorOnSources(errorCollector, c.allSources)(s"Could not find path [${uri.getPath}] in site")
           }
         case absolute if validateAbsolute =>
-          validateExternalLink(absolute, errorCollector, logger)
+          validateExternalLink(absolute, retryCount, errorCollector, logger)
         case _ =>
         // Ignore
       }
@@ -160,20 +161,29 @@ class ParadoxProcessor(reader: Reader = new Reader, writer: Writer = new Writer,
     errorCollector.errorCount
   }
 
-  private def validateExternalLink(capturedLink: CapturedLink, errorContext: ErrorContext, logger: ParadoxLogger) = {
+  private def validateExternalLink(capturedLink: CapturedLink, retryCount: Int, errorContext: ErrorContext, logger: ParadoxLogger) = {
     logger.info(s"Validating external link: ${capturedLink.link}")
 
     def reportError = reportErrorOnSources(errorContext, capturedLink.allSources)(_)
     val url = capturedLink.link.toString
 
     try {
-      val response = Jsoup.connect(url)
+      def tryConnect = Jsoup.connect(url)
         .userAgent("Paradox Link Validator <https://github.com/lightbend/paradox>")
         .followRedirects(false)
         .ignoreHttpErrors(true)
         .ignoreContentType(true)
         .execute()
 
+      @tailrec
+      def validateWithRetries(retryCount: Int): Connection.Response = {
+        val res = tryConnect
+        if (retryCount == 0 || res.statusCode() == 200) res
+        else validateWithRetries(retryCount - 1)
+      }
+
+      val response = validateWithRetries(retryCount)
+
       // jsoup doesn't offer any simple way to clean up, the only way to close is to get the body stream and close it,
       // but if you've already read the response body, that will throw an exception, and there's no way to check if
       // you've already tried to read the response body, so we can't do that in a finally block, we have to do it

docs/src/main/paradox/validation.md

@@ -53,3 +53,11 @@ paradoxValidationIgnorePaths ++= Seq(
   "/docs/version/(?!latest).*"
 )
 ```
+
+## Retrying links check
+
+`paradoxValidateLinksRetryCount` setting allows retrying link check for the provided number of times in case link returns non success response code i.e., other than 200 status code. 
+
+```scala
+paradoxValidateLinksRetryCount := 3 // retries link check 3 times in case of non 200 response code
+```

plugin/src/main/scala/com/lightbend/paradox/sbt/ParadoxKeys.scala

@@ -52,6 +52,7 @@ trait ParadoxKeys {
   val paradoxBrowse = taskKey[Unit]("Open the docs in the default browser")
   val paradoxValidateInternalLinks = taskKey[Unit]("Validate internal, non ref paradox links.")
   val paradoxValidateLinks = taskKey[Unit]("Validate all non ref paradox links.")
+  val paradoxValidateLinksRetryCount = taskKey[Int]("Number of retries for validate links task.")
   val paradoxValidationIgnorePaths = settingKey[List[Regex]]("List of regular expressions to apply to paths to determine if they should be ignored.")
   val paradoxValidationSiteBasePath = settingKey[Option[String]]("The base path that the documentation is deployed to, allows validating links on the docs site that are outside of the documentation root tree")
   val paradoxSingle = taskKey[File]("Build the single page HTML Paradox site")

plugin/src/main/scala/com/lightbend/paradox/sbt/ParadoxPlugin.scala

@@ -65,6 +65,7 @@ object ParadoxPlugin extends AutoPlugin {
     paradoxLeadingBreadcrumbs := Nil,
     paradoxGroups := Map.empty,
     libraryDependencies ++= paradoxTheme.value.toSeq map (_ % ParadoxTheme),
+    paradoxValidateLinksRetryCount := 0,
     paradoxValidationIgnorePaths := List("http://localhost.*".r),
     paradoxValidationSiteBasePath := None
   )
@@ -378,6 +379,7 @@ object ParadoxPlugin extends AutoPlugin {
       paradoxGroups.value,
       paradoxProperties.value,
       paradoxValidationIgnorePaths.value,
+      paradoxValidateLinksRetryCount.value,
       validateAbsolute,
       new SbtParadoxLogger(strms.log)
     )